The present invention relates to new pyrazoline derivatives, of general formula (I), and to physiologically acceptable salts thereof, to the procedures for their preparation, to their application as medicaments in human and or veterinary therapy and to the pharmaceutical composition that contain them. 
The new compounds object of the present invention can be used in the pharmaceutical industry as intermediates and for the preparation of medicaments.
Non-steroid anti-inflammatory drugs (NSAIDS) are traditionally classified as anti-inflammatory, antipyretic and analgesic agents for the symptomatic alleviation of inflammation, fever and light to moderate pain. The main indications for these drugs are osteoarthritis, rheumatoid arthritis and other inflammatory diseases of articulations, as well as for the treatment of inflammations associated with small lesions and as analgesics of broad use. The NSAIDS are essentially inhibitors of acute inflammatory response, but in rheumatic disorders they have little effect on the underlying degenerative changes occurring in tissue.
The discovery of the main mechanism of action of the NSAIDS by inhibition of cyclooxygenase (COX) [J. R. Vane, Nature, 1971, 231, 232] provided a satisfactory explanation of their therapeutic action and established the importance that certain prostaglandins have as mediators in inflammatory disease [R. J. Flower, J. R. Vane, Biochem. Pharm., 1974, 23, 1439; J. R. Vane, R. M. Botting, Postgrad Med. J., 1990, 66(Suppl 4), S2]. The gastric toxicity of the classic NSAIDS, as well as their beneficial effects, is due to the suppression of prostaglandin synthesis by inhibition of the COX enzyme. Although several strategies have been followed (enteral Coating to prevent adsorption in the stomach, parenteral administration, pro-drug formulation, etc) to reduce the gastrointestinal lesions provoked by the NSAIDS, none of these modifications have provided a significant impact on the incidence of serious adverse reactions such as perforation and haemorrhaging.
The discovery of an induced prostaglandin-synthetase, denominated cyclooxygenase-2 (COX-2), different from the constitutive enzyme, currently denominated cyclooxygenase-1 (COX-1) [J. Sirois, J. R. Richards, J. Biol. Chem., 1992, 267, 6382], has renewed the interest in the development of new anti-inflammatory drugs. The identification of the isoform COX-2 has led to the hypothesis that it could be responsible for the production of prostaglandins in places where inflammation occurs. As a result, selective inhibition of this isoenzyme would reduce the inflammation without producing the side effects of gastric and renal toxicity. The COX-1 isoenzyme is essentially expressed in most of tissues with the function of synthesising prostaglandins which regulate the normal cell activity. On the other hand, the isoenzyme COX-2 is not normally present in cells but in chronic inflammation the levels of the protein COX-2 increase in parallel with the over-production of prostaglandins [J. R. Vane, R. M. Botting, Infalmm. Res., 1995, 44, 1]. Therefore, a selective COX-2 inhibitor has the same anti-inflammatory, antipyretic and analgesic properties as a conventional non-steroid anti-inflammatory agent and also inhibits the uterine contractions induced by hormones and presents potential anti-carcinogenic effects and beneficial effects in the prevention of the development of Alzheimer disease. On the other hand, a selective COX-2 inhibitor reduces the potential gastrointestinal toxicity, reduces the potential renal side effects and reduces the effects of bleeding time.
The tri-dimensional structure of COX-1 has been determined by x-ray diffraction [D. Picot, P. J. Loll, R. M. Garavito, Nature, 1994, 367, 243]. Three of the helixes of the structure form the entrance to the cyclooxygenase channel and its insertion in the membrane allows the arachidonic acid to access the active site from inside the bilayer. The active site of cyclooxygenase is a large hydrophobic channel and the authors argue that the NSAIDS inhibit COX-1 by excluding arachidonic acid from the upper part of the channel. Recently [R. S. Service, Science, 1996, 273, 1660], the three-dimensional structure of COX-2 has been described, which allows comparison of the similarities and differences between the two isoforms and therefore study of new drugs that selectively inhibit COX-2. The structures of COX-1 and COX-2 show that the sites where the anti-inflammatory agents bind to the enzymes are very similar but there is a difference of at least one important amino acid. A voluminous isoleucine present in the active site of COX-1 is replaced by a valine in COX-2. The isoleucine blocks the lateral cavity that is separated from the principle bond of both isoenzymes. The blocked cavity of COX-1 does not impede the binding of classic NSAIDS, but an inhibitor that needs the extra support point supplied by the lateral cavity will bind more easily to COX-2 than to COX-1. As a result, a model for a new generation of anit-inflammatory agents is one where the inhibitors of cyclooxygenase have a large preference for the lateral cavity of COX-2.
In the chemical literature derivatives of nitrogenated heterocyclic aromatics of five members have been described with COX-2 inhibitory activity. Within these azole derivatives are the pyrrols [W. W. Wilkerson, et al, J. Med. Chem., 1994, 37, 988; W. W. Wilkerson, et al, J. Med. Chem., 1995, 38, 3895; I. K. Khanna, et al, J. Med. Chem., 1997, 40, 1619], pyrazoles [T. D. Penning, et al, J. Med. Chem., 1997, 40, 1347; K. Tsuji, et al, Chem. Pharm. Bull., 1997, 45, 987; K. Tsuji, et al, Chem. Pharm. Bull., 1997, 45, 1475], or imidazoles [Khanna, et al, J. Med. Chem., 1997, 40, 1634].
We have now discovered that the novel compounds derived from pyrazolines of general formula (I) show interesting biological properties and these make them particularly useful for their employment in human and/or veterinary therapy. The compounds object of this invention are useful as agents with anti-inflammatory activity and for other diseases in which cyclooxygenase-2 plays a part, without having the gastric and renal toxicity of the classic NSAIDS.
The present invention provides new pyrazolines that inhibit the enzyme cyclooxygenase-2, with application in human and/or veterinary medicine as anti-inflammatories and for other diseases in which cyclooxygenase-2 plays a part, and that have low or no gastric and renal toxicity. These anti-inflammatories therefore have a better safety profile. The new compounds object of the present invention are derivatives of xcex942-pyrazolines, also known as 4,5-dihydro-1H-pyrazoles. They are therefore nitrogenated heterocyclic compounds. As a result the pyrazoline rings are not planar as opposed to the azoles described previously. The compounds object of the present invention have the general formula (I) 
wherein
R1 represents a hydrogen atom, a methyl, fluoromethyl, difluormethyl, trfluoromethyl, carboxylic acid, lower carboxylate of 1 to 4 carbon atoms, carboxamide or cyano group,
R2 represents a hydrogen or methyl group,
R3, R4, R7 and R8, identical or different, represent an atom of hydrogen, chlorine, fluorine, a methyl, trifluoromethyl or methoxy group,
R5 represents an atom of hydrogen, chlorine, fluorine, a methyl, trifluoromethyl or methoxy group, provided thatxe2x80x94in all casesxe2x80x94R6 represents a methylsulphonyl, aminosulphonyl or acetoaminosulphonyl group,
R6 represents an atom of hydrogen, chlorine, fluroine, a methyl, trifluromethyl or methoxy group, provided that xe2x80x94in all casesxe2x80x94R5 represents a methylsulphonyl, aminosulphonyl or acetoaminosulphonyl group.
For the case that R1 represents a methyl group
R2 represents a hydrogen atom or a methyl group,
R3 y R8, identical or different, represent an atom of hydrogen, chlorine, fluorine, a methyl or trifluoromethyl group,
R4 represents a hydrogen, fluorine atom, a methyl, trifluoro-methyl or methoxy group,
R5 represents a fluorine atom, a triflouromethyl or trifluoromethoxy group, providedxe2x80x94in all casesxe2x80x94that R6 represents a methylsulphonyl or aminosulphonyl,
R6 represents a hydrogen, chlorine, fluorine atom, a methyl, trifluoromethyl, methoxy or trifluoromethoxy group, providedxe2x80x94in all casesxe2x80x94that R5 represents a methylsulphonyl or aminosulphonyl, and
R7 represents a hydrogen, chlorine, fluorine atom, a methyl, trifluoromethyl or methoxy group.
The new compounds of general formula (I) have an asymmetric carbon atom and so can be prepared enantiomerically pure or as racemates. The racemates of compounds (I) can be resolved into their optical isomers by conventional methods, such as separation by chiral stationary phase chromatography for example, or by fractionated crystallisation of its diastereoisomeric salts, which can be prepared by reacting the compounds (I) with enantiomerically pure acids. Similarly, they can also be obtained by enantioselective synthesis using enantiomerically pure chiral precursors.
The present invention also relates to the physiologically acceptable salts of the compounds of general formula (I), in particular, to the addition salts formed with mineral acids such as hydrochloric, hydrobromic, phosphoric, sulphuric, nitric acid, etc, and with organic acids such as citric, maleic, fumaric acid, tartaric acids or its derivatives, p-toluenesulphonic, methanosulphonic, camphosulphonic acid etc.
The novel derivatives of general formula (I) can be used in mammals, including man, as anti-inflammatory agents for the treatment of inflammation and for the treatment of other disorders associated with inflammation, such as analgesics for the treatment of pain and migraine, and as anti-pyretics in the treatment of fever. For example, the new derivatives of general formula (I) can be used in the treatment of arthritis, including but limited to the treatment of rheumatoid arthritis, spondyloarthropathies, gouty arthritis, systemic lupus erythematosus, osteoarthritis and juvenile arthritis. The novel derivatives of general formula (I) can be used in the treatment of asthma, bronchitis, menstrual disorders, tendinitis, bursitis and different states that affect the skin such as psoriasis, eczema, burns and dermatitis. The novel derivatives of general formula (I) can also be used in the treatment of gastrointestinal afflictions such as syndrome of inflamed intestine, Crohn""s disease, gastritis, irritated colon syndrome and ulcerous colitis.
The novel derivatives of general formula (I) can be prepared, in accordance with the invention, following the methods that are indicated below:
Method A
The preparation of the compounds of general formula (I) is carried out by reacting a compound of general formula (II) 
wherein R1 represents a hydrogen atom, a methyl, fluoromethyl, difluoromethyl, trifluoromethyl and carboxylic acid groups, and R2, R3, R4 and R5 have the same meaning as that indicated for general formula (I), with a phenylhydrazine of general formula (III) in base or salt form 
wherein R6, R7 and R8 have the same meaning as that described previously for general formula I.
The reaction is carried out in the presence of a suitable solvent such as, for example, alcohols such as methanol, ethanol, ethers such as dioxane, tetrahydrofuran, or mixtures thereof or other solvents. The reaction takes place in acid medium, that can be organic, such as acetic acid, for example, or inorganic such as hydrochloric acid for example, or a mixture of the two, or in a base medium such as piperidine, piperazine, sodium hydroxide, potassium hydroxide, sodium methoxide or sodium ethoxide for example, or a mixture thereof. The acidic or base medium itself can act as a solvent. The most suitable temperatures vary between room temperature and the reflux temperature of the solvent and the reaction times can lie between several hours and several days.
Method B
The preparation of the compounds of general formula (I), wherein R1 represents an alkyl carboxylate with less than 1 to 4 carbon atoms and R2, R3, R4, R5, R6, R7 and R8 have the same meaning as that given above, is effected by reacting a compound of general formula (I) wherein R1 represents a carboxylic acid group (COOH) and R2, R3, R4, R5, R6, R7 y R8 have the same meaning as that given above, with a suitable reagent to form the acid chloride such as thionyl chloride or oxalyl chloride for example, and then carrying out an esterification reaction with an aliphatic alcohol of 1 to 4 carbon atoms in the presence of an organic base, such as triethylamine or pyridine, or by direct reaction of carboxylic acid with the corresponding saturated anhydrous alcohol with gaseous hydrogen chloride. The reaction is carried out in the reagent as its own solvent or in other appropriate solvents such as halogenated hydrocarbons such as dichloromethane, chloroform or carbon tetrachloride, ethers such as dioxane, tetrahydrofruan, ethyl ether or dimethoxyethane. The most appropriate temperatures vary between 0xc2x0 C. and the reflux temperature of the solvent and the reaction times lie between ten minutes and 24 hours.
Method C
The preparation of the compounds of general formula (I), wherein R1 represents a carboxamide group and R2, R3, R4, R5, R6, R7 and R8 have the same meaning as that indicated above, is carried out be reacting a compound of general formula (I) in which R1 represents a carboxylic acid group (COOH) and R2, R3, R4, R5, R6, R7 and R8 have the same meaning as that indicated above, with a suitable reagent for forming the corresponding acid chloride, for example, thionyl chloride or oxalyl chloride and then reacting with ammonia, that can be in the form of concentrated aqueous solution or dissolved in a suitable solvent. The reaction is carried out in a suitable solvent such as, for example, ethers such as dioxane, tetrahydrofuran, ethyl ether or dimethoxyethane. The most suitable temperatures vary between 0xc2x0 C. and the reflux temperature of the solvent and the reaction times lie between 1 and 24 hours.
Method D
The preparation of the compounds of general formula (I), wherein R1 represents a cyano group and R2, R3, R4, R5, R6, R7 y R8 have the same meaning as that indicated above, is carried out by reacting a compound of general formula (I) wherein R1 represents a carboxamide group and R2, R3, R4, R5, R6, R7 and R8 have the same meaning as that indicated above, with a suitable reagent such as, for example, the thionyl dimethylformamide-chloride or methanosulphonyl chloride. The reaction is carried out in a suitable solvent such as, for example, dimethylformamide or pyridine. The most suitable temperatures vary between 0xc2x0 C. and the reflux temperature of the solvent and the reaction times lies between fifteen minutes and 24 hours.
Method E
The compounds of general formula (II), intermediates in the preparation of the compounds of general formula (I), are commercially available or can be obtained using different known methods among which the following are found:
Method E-1
The preparation of the compound of general formula (II), wherein R1 represents a mono- di- or trifluoromethyl group, R2 represents a hydrogen atom and R3, R4 and R5 have the same meaning indicated above for the compounds of general formula (I), is carried out by reaction of a benzaldehyde of general formula (IV) 
wherein R3, R4 and R5 have the same meaning as that given above for the general formula (I), with N-phenyl(mono, di or trifluoro)acetimidoyl chloride in the presence of a dialkyl phosphonate, such as phosphonate or diethylmethyl, and a strong organic base, such as LDA (lithium diisopropylamide), or by the Wittig reaction with mono-, di- or trifluoroacetylmethylenetriphenylphosphorane and a base such as sodium carbonate or potassium carbonate. The reaction is carried out in a suitable solvent such as, for example, dichloromethane, chloroform or benzene, or an ether such as tetrahydrofurane, ethyl ether, dimethoxyethane or dioxane. The most suitable temperatures vary between xe2x88x9270xc2x0 C. and the reflux temperature of the solvent, and the reaction times lie between fifteen minutes and twenty hours.
Method E-2
The preparation of the compounds of general formula (II), in which R1 represents a methyl or trifluoromethyl group, R2 represents a methyl group and R3, R4 and R5 have the same meaning indicated above for the compounds of general formula (I), is carried out be reacting a compound of general formula (V) 
wherein R2 represents a methyl group and R3, R4 and R5 have the same meaning as that indicated above for the compounds of general formula (I), with mono-, di- or trifluoroacetic anhydride in the presence of the complex dimethyl sulphide-boron trifluoride. The reaction is carried out in a suitable solvent such as, for example, halogenated hydrocarbons such as dichloromethane, chloroform or carbon tetrachloride or ethers such as dioxane, tetrahydrofuran, ethyl ether or dimethoxyethane. The most suitable temperatures vary between xe2x88x9270xc2x0 C. and the reflux temperature of the solvent, and the reaction times lie between twenty minutes and twenty hours.
Method E-3
The preparation of compounds of general formula (II), in which R1 represents a methyl or trifluorometyl group, R2 represents a hydrogen atom and R3, R4 and R5 have the same meaning as that indicated previously for the compounds of general formula (I), are carried out by different procedures among which can be found, for example, the Claisen-Schmidt reaction between benzaldehyde of general formula (IV) and acetone or 1,1,1-trifluoroacetone in presence of an aqueous solution of alkaline metal hydroxide such as sodium hydroxide or potassium hydroxide or acetic acid and piperidine; the Wittig-Horner reaction between a benzaldehyde of general formula (IV) and a 2-oxo-alkyl phosphonate in the presence of an aqueous solution of a base such as, for example, potassium carbonate or potassium bicarbonate; the reaction of a benzaldehyde of general formula (IV) with xcex1,xcex1-bis(trimethylsilyl)-t-butylketimine in the presence of a Lewis acid such as zinc dibromide for example or by reaction of a compound of general formula (VI) 
wherein R3, R4 and R5 have the same meaning as that indicated above for the general formula (I), with trimethylaluminium in the presence of aluminium trichloride.
The reaction is carried out in a suitable solvent such as, for example, an alcohol such as methanol or ethanol, a halogenated hydrocarbon such as carbon tetrachloride, chloroform or dichloromethane, an ether such as tetrahydrofuran, ethyl ether, dioxane or dimethoxyethane, water or a mixture thereof. The reaction temperature can vary between xe2x88x9260xc2x0 C. and the reflux temperature of the solvent and the reaction times can vary between two hours and several days.
Method E-4
The preparation of compounds of general formula (II), wherein R1 and R2 represent a hydrogen atom and R3, R4 and R5 have the same meaning as that indicated above for the compounds of general formula (I), are carried out following different methods among which can be found, for example, the Wittig-Homer reaction with a benzaldehyge of general formula IV and then reducing the unsaturated xcex1,xcex2 ester with a metal hydride such as diisobutylaluminum hydride (Dibal); by reaction of a benzaldehyde of general formula IV with xcex1,xcex1-bis(trimethylsilyl)-t-butylacetaldimine in the presence of a Lewis acid such as zinc dibromide or by condensation of a benzaldehyde of general formula IV with acetaldehyde in the presence of a alkaline metal hydroxide such as sodium hydroxide or potassium hydroxide.
Method F
The preparation of the compounds of general formula (I), wherein R1, R2, R3, R4, R7 and R8 have the same meaning as that indicated above and R5 represents a hydrogen, chlorine, fluorine atom, a methyl, trifluoromethyl, methoxy or trifluoromethoxy group, providedxe2x80x94in all casesxe2x80x94that R6 represents an acetylaminosulphonyl group, or R6 represents a hydrogen, chlorine, fluorine atom, a methyl, trifluoromethyl, methoxy or trifluoromethoxy group, providedxe2x80x94in all casesxe2x80x94that R5 represents an acetylaminosulphonyl group, is carried out by reacting a compound of general formula (I) wherein R1, R2, R3, R4, R7 and R8 have the same meaning as that indicated above and R5 represents a hydrogen, chlorine, fluorine atom, a methyl, trifluoromethyl, methoxy or trifluoromethoxy group, providedxe2x80x94in all casesxe2x80x94that R6 represents an aminosulphonyl group, or R6 represents a hydrogen, chlorine, fluorine atom, a methyl, trifluoromethyl, methoxy or trifloromethoxy group, provided, in all cases, that R5 represents an aminosulphonyl group, with a suitable reactant such as, for example, acetyl chloride or acetic anhydride. The reaction is carried out in the absence of solvent, or in a suitable solvent such as, for example, dimethylformamide or pyridine. The most suitable temperatures vary between 0xc2x0 C. and the reflux temperature and the reaction times lie between 15 minutes and 14 hours.